OSLO -- Talks on extending a U.N.-led fight against global warming beyond 2012 may last until 2010 to allow a wider U.S. role after President George W. Bush steps down, a U.N. expert said on Wednesday.

Many environmentalists, and some governments, want a new pact on cutting greenhouse emissions agreed by 2008 to give businesses and investors time to adapt to new rules after the U.N. Kyoto Protocol's first period ends in 2012.

"I sense in the rhetoric that people are talking more about 2009 (than 2008)", said Michael Zammit Cutajar, a climate expert from Malta who leads a U.N. group looking at how to extend Kyoto.

"We need a deal that includes Kyoto and includes the United States," he told Reuters during a conference in Oslo on carbon dioxide emissions.

"I wouldn't be surprised, given the U.S. electoral calendar, if the overall deal would be 2010," he said. The United States is the main source of greenhouse gas emissions, mainly from fossil fuels burned in power plants, factories and cars.

Bush, who steps down in January 2009 after two terms in office, pulled out of Kyoto in 2001 on grounds the U.S. economy would be damaged by its caps on emissions of greenhouse gases.

He said Kyoto wrongly excluded developing nations and has instead stressed big investments in new technologies, such as non-polluting hydrogen or filtering greenhouse gases from the emissions of coal-burning power plants.

FIRST STEP

Kyoto obliges 35 developed nations to cut emissions by 5.2 percent below 1990 levels by 2008-12 as a small first step to curb warming that many scientists say will cause more heatwaves, desertification, erosion and rising sea levels.

Environment ministers from round the world will meet in Nairobi from Nov. 6-17 for talks searching for ways to extend and widen the pact and to help developing nations adapt to the damaging impact of climate change.

Among ideas beyond Kyoto, Zammit Cutajar said rich nations were showing interest in sectoral targets for global industries beyond 2012, such as emissions limits for aluminium or cement makers.

He praised Bush for big investments in clean energies but noted California and several northeastern U.S. states were taking steps to bypass Washington by setting their own greenhouse gas limits.

"The logic of the Kyoto Protocol seems to have taken root in parts of the USA," he said. "Will that movement start to influence the centre after 2008? I would hazard a guess that it would."

Zammit Cutajar, a former head of the U.N.'s climate change secretariat, was appointed in May as head of a U.N. working group on new commitments under the Kyoto Protocol.

He said U.S. involvement in capping emissions could also encourage big developing nations, such as China or India, to look at ways to brake the rise of their emissions.

No countries are proposing developing nations adopt Kyoto-style caps on their emissions from 2012, he said.

He said the Nairobi talks would also look at proposals for forests to be planted or preserved from logging as part of a fight against global warming. Plants soak carbon dioxide, the main greenhouse gas, as they grow.